The music fest, set for Sunday, Sept. 10 at the Merriweather Post Pavilion (10475 Little Patuxent Parkway, Columbia, Md.), features an impressive lineup this year, including TV on the Radio, The Black Keys, Cee Lo Green, Deadmau5, Two Door Cinema Club and more.

The FreeFest benefits groups that help at-risk and homeless youth. If you volunteer with one of the groups, you'll earn your free ticket. Volunteer events include making toiletry kits and bag lunches for the homeless, back-to-school kits for kids, drives for school supplies and more. See all planned volunteer events here.

Of course, you can also shell out $49.50 for a paid ticket (which includes a T-shirt, poster and donation), but where's the fun in that?